Filament supports for electric lamps



July 13, 1965 R. H. HOLCOMB 3,195,002

FILAMENT SUPPORTS FOR ELECTRIC LAMPS Filed Sept. 19, 1962 Inveant'or. Richard H. Hotcomb 3 /Z/ His Atir ne3 r' 3,195,002 Patented July 13, 1965 3,195,002 FILAMENT SUPPORTS FOR ELECTRIC LAMPS Richard H. Holcomb, South Euclid, Ohio, assignor to General Electric Company, a corporation of New York Filed Sept. 19, 1962, Ser. No. 224,743 4 Claims. (Cl. 313-279) This invention relates to electric incandescent lamps, and more particularly to tubular double-ended lamps comprising an elongated tubular envelope having a helically coiled filament extending axially thereof. Still more particularly, the invention relates to improved means for supporting the filament in the axis of the envelope.

One form of support which has come into extensive use is that disclosed and claimed in U.S. Patent 2,813,- 933, Fridrich, and which comprises a sheet metal wafer or disc which is disposed transversely between successive turns of the filament coil. The disc is pierced interiorly of the filament coil to form a central aperture with a collar portion at the margin thereof engaging the inner side of an adjacent coil turn to hold the disc against lateral displacement. A series of such discs are conveniently formed and attached to the filament by the method and apparatus disclosed and claimed in US. Patent 2,813,- 327, Fridrich.

Such disc supports have proved to be quite satisfactory so long as the filament coil is of a close pitch as is ordinarily the case, the disc of some .002 or .003 inch thickness .being wedged between the coil turns and crimped to the inside of one of the turns. occasions where it is desirable to use .a filament coil of relatively open pitch where-in the spacing between turns exceeds the thickness of the disc. In such cases, the discs are easily loosened so that they tilt and even fall off the coil.

It is accordingly an object of the invention to provide a filament support structure which retains the advantages of -a disc form of support member but which is firmly attached to the filament.

Briefly stated, in accordance with the invention, the stated object is achieved by a double-disc structure wherein a pair of discs are slightly separated so as to be on opposite sides of a coil turn, and the discs are secured together at their peripheries, for example by spot welding, at a number of points sufficient to firmly clamp the discs to the said coil turn.

Further features and advantages of the invention will appear from the following detailed description and from the drawing wherein:

FIG. 1 is a side view of a lamp embodying the invention;

FIG. 2 is a fragmentary section of a filament coil and associated disc structure;

FIG. 3 is a perspective view of the disc and filament assembly shown in FIG. 2; and

FIG. 4 is an elevation of a modified disc structure.

Referring to FIG. 1, the lamp shown therein, by way of example, is of the infrared or heat lamp type described and claimed in Patent 2,864,025, Foote et al. The lamp comprises a gas filled tubular quartz envelope 1 'having a pinch seal 2 at each end thereof through which extends a lead-in conductor comprising inner and outer wire sections 3 and 4 and an intermediate ribbon or foil section 5 hermetically embedded in the pinch seal. A helically coiled filament 6 of tungsten wire extends axially of the envelope 1 and is supported therein by a plurality of spaced disc member-s 7 of tantalum or other suitable refractory metal. The said filament 6 is of relatively open pitch; it may for example be composed of tungsten wire of .014 inch diameter wound to a pitch of 208%, where pitch is defined as the ratio of distance between centers of adjacent coil turns to wire diameter. In other words,

However, there are in the present case the spacing between coil turns is somewhat greater than the wire diameter.

In accordance with the invention each of the disc structures 7 consists of a pair of individual discs 8 and 9 located at opposite sides of a turn 10 of the coil 6, and the discs are preferably of the form disclosed in the aforesaid U.S. Patent 2,813,993. Accordingly, each discis provided with .a passageway or opening'in the form of a radial slit -11 which extends inwardly of the disc from its periphery and through which slit the filament wire passes, as shown in FIG. 3. inwardly of the disc a distance sufficient to permit the concentric positioning of the disc relative to the filament coil 6, with the filament wire received or caught in the slit. To facilitate the insertion of the filament Wire into the slit 1 1, the outer end of the slit is flared outwardly as indicated at 12. 7

Each disc 8 and 9 is held in place on the coil 6 by a collar portion 13 at the margin of a central opening 14 in the disc and within the interior of the coil. The collar portion 13 is preferably formed in the manner disclosed in the aforesaid US. Patent 2,813,327, by piercing the disc, or a metal strip from which the disc is punched, with a pointed piercing tool or mandrel inserted through the interior of the filament coil. The piercing tool may be shaped to form a split collar 13 composed of -a plurality of tongues or tabs 15 which are partially wrapped around the inner side of an adjacent coil turn.

Due to the relatively great pitch of the coil 6, whereby the spacing between coil turns exceeds the thickness of the discs 8 or 9, the individual discs are not clamped to the adjacent coil turn sufiiciently firmly to prevent loosening and tilting. Therefore, in accordance with the invention, a pair of discs are slightly separated from each other to be at opposite sides of a coil turn 10, and the discs are secured together at their peripheries to firmly clamp them to the coil. The securing together of the discs may be achieved by spot welding. Welding at two diametrically opposed points has proved to be suflicient to firmly clamp the discs to the filament.

The disc structure 7 shown in FIG. 4 is like that shown in .FIGS. 2 and 3 except that the formation of the central aperture 14 and collar portion 13 is omitted. In that event, in order to avoid loosening or removal of the pair of discs from the filament coil 6 by lateral movement, the discs 8' and 9' are arranged with their-respective slits 11' out of alignment.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, in an incandescent lamp comprising a hermetically sealed envelope containing a helically coiled lamp filament of refractory wire and a support member comprising a pair of refractory sheet metal discs disposed transversely of the coil and at opposite sides of a turn of said coil, said discs :being of sheet metal substantially thinner than the spacing between turns of said coiled filament wire, said discs being secured together at their peripheries at a number of points sufiicient to firmly clamp them to said coil turn.

2. In combination, in an incandescent lamp comprising a hermetically sealed envelope containing a helically coiled lamp filament of refractory wire and a support member comprising a pair of refractory sheet metal discs disposed transversely of the coil and at opposite sides of a turn of said coil, said discs being of sheet metal substantially thinner than the spacing between turns of said coiled filament wire, said discs being spot welded together at their peripheries at a number of points sutficient to firmly clamp them to said coil turn.

3. In combination, in an incandescent lamp compris ing a hermetically sealed envelope containing .a helically The slit 11 extends.

coiled lamp filament of refractory wire and a support member comprising a pair of refractory sheet metal discs disposed transversely of the coil and at opposite sides of a turn of said coil, said discs being of sheet metal substantially thinner than the spacing between turns of said coiled filament Wire, each said disc having a central aperture therein and a collar portion at the margin of said aperture within the interior of the coil, said discs being secured together at their peripheries at a number of points suflicient to firmly clamp them to said coil turn.

4. In combination, in an incandescent lamp comprising a hermetically sealed envelope containing a hel-ically coiled lamp filament of refractory wire and a support member comprising a pair of refractory sheet metal discs each having an opening extending inwardly from its periphery, said discs being inserted at opposite sides of a turn of said filament and disposed transversely of said filament so that parts of adjacent turns pass through respective openings in said discs, said discs being of sheet metal substantially thinner than the spacing between turns of said coiled filament wire, said discs being secured together at their peripheries at a number of points suificient to firmly clamp them to the filament turn located therebetween.

References Cited by the Examiner UNITED STATES PATENTS 2,813,993 11/57 Fridrich 313279 FOREIGN PATENTS 632,937 7/36 Germany. 470,760 8/37 Great Britain.

DAVID J. GALVIN, Primary Examiner.

JAMES D. KALLAM, Examiner. 

1. IN COMBINATION, IN AN INCANDESCENT LAMP COMPRISING A HERMETICALLY SEALED EVELOPE CONTAINING A HELICALLY COILED LAMP FILAMENT OF REFRACTORY WIRE AND A SUPPORT MEMBER COMPRISING A PAIR OF REFRACTORY SHEET METAL DISCS DISPOSED TRANSVERELY OF THE COIL AND AT OPPOSITE SIDES OF A TURN OF SAID COIL, SAID DISCS BEING OF SHEET METAL SUBSTANTIALLY THINNER THAN THE SPACING BETWEEN TURNS OF SAID COILED FILAMENT, WIRE, SAID DISCS BEING SECURED TOGETHER AT THEIR PERIPHERIES AT A NUMBER OF POINTS SUFFICIENT TO FIRMLY CLAMP THEM TO SAID COIL TURN. 